The present invention relates to a control apparatus of an automated manual transmission mounted on a motor vehicle or the like, and more particularly to the apparatus effectively applied to an automated manual transmission having a plurality of transmission gear trains.
A manual type transmission executing a shift change operation by a manual operation of a driver includes an input shaft engaged to an engine and to which a plurality of drive gears are attached, and an output shaft engaged to drive wheels and to which a plurality of driven gears forming pairs together with the drive gears are attached, in which a plurality of transmission gear trains are provided between the input shaft and the output shaft. In this manual type transmission, a gear change operation, i.e., a shift change is performed by manually switching a switching mechanism such as a synchromesh mechanism for switching a transmission gear train performing a power transmission, namely, a gear pair among a plurality of transmission gear trains after disengaging a clutch at a time of changing gear, thereafter engaging the clutch.
When automatically executing the shift change and the clutch operation by a hydraulic actuator, it is possible to obtain an automated manual transmission based on a structure of a manual type transmission. This automated manual transmission has an advantage that the number of the parts can be reduced in comparison with a normal torque converter type automatic transmission having a planetary gear or the like in an automatic shift change mechanism to easily lighten the transmission, and a further advantage that a transmission efficiency of a drive system is higher than that of the automatic transmission.
The automated manual transmission is provided with a main clutch positioned between a crank shaft and the input shaft in order to switch between an engaged state and a disengaged state. As the main clutch, a wet clutch may be employed which is superior to a dry clutch in durability and controlling characteristic. The wet clutch performs a connection and disconnection of power due to pressing a drive side clutch disc fixed to the crank shaft against a driven side clutch disc fixed to the input shaft or not.
However, there occurs a drag torque due to fluid friction of lubricating oil while disengaging the clutch since the lubricating oil is filled between the drive side clutch disc and the driven side clutch disc. Therefore, a rotational speed of the input shaft at a time of down-shifting of the automated manual transmission with the wet clutch results in extremely falling due to the drag torque of the wet clutch when turning a throttle valve of the engine down at the same time as disengaging the wet clutch at the time of down-shifting. Thereby, the difference of the rotational speed between the input shaft and the output shaft becomes large, so that a load applied to a synchromesh mechanism becomes excessive. As a result, there occur problems that shift changing time may be extended, or the synchromesh mechanism may be damaged. In particular, such a tendency is strong at a low temperature oil since viscosity of the lubricating oil becomes large.
In order to improve these disadvantages, for example, the Japanese Patent No. 2873690 discloses a structure that a lubricating circuit of the wet clutch is provided with a valve to discharge the lubricating oil within the wet clutch at a time of shift change. Indeed, discharge of the lubricating oil results in reducing the drag torque, but complicated lubricating paths are needed for doing so, so that there may occur any further problem in an aspect of space or cost.
An object of the present invention is to improve a transmission characteristic of a vehicular automated manual transmission provided with a wet clutch.
In accordance with the present invention, there is provided a control apparatus of a vehicular automated manual transmission having an input shaft provided with a plurality of drive gears, an output shaft provided with a plurality of driven gears engaging with the drive gears, and a hydraulic actuator for switching a transmission gear trains transmitting a power from the input shaft to the output shaft, comprising an electronic control throttle valve for adjusting an engine speed, a wet clutch for engaging/disengaging an engine with the input shaft, the wet clutch being provided between the engine and the input shaft, and control means for setting the engine speed higher by a predetermined value than a rotational speed of the input shaft through allowing the electronic control throttle valve to open when down-shifting the transmission gear trains by the actuator.
It is a further characteristic of the present invention that the control means adjusts an opening degree of the throttle valve based on signals detected from an engine speed sensor, an input shaft rotational speed sensor, and a lubricating oil temperature sensor.
In addition, it is the other characteristic of the present invention that the predetermined value is set small as an oil temperature of a lubricating oil filled in the wet clutch becomes low.
According to the present invention, a transmission characteristic of the vehicular automated manual transmission with the wet clutch can be improved, in particular, during down-shifting. In more detail, since the engine speed is set higher by the predetermined value than the input shaft rotational speed, in which the drag torque of the wet clutch works in such a manner that the rotation of the input shaft is increased, the difference of the rotational speed between the input shaft and output shaft becomes small, so that the transmission operation of down-shifting can be quickly executed. In addition, it is possible to reduce the degree of shock which occurs when the wet clutch is engaged again after terminating the down-shifting operation. Further, the load applied to the synchromesh mechanism can be reduced, so that it is possible to prevent the synchromesh mechanism from being damaged due to the load.
Also, since the added predetermined value is set in accordance with the lubricating oil temperature, the viscosity of the lubricating oil, i.e., force of drag torque thereof can be considered in the transmission control of the present invention.